Association of genetic polymorphisms with differential catalase gene expression in prognostic groups of chronic lymphocytic leukemia patients.

Chronic lymphocytic leukemia (CLL) is characterized by a highly variable clinical course, with some patients having indolent disease and others experiencing a more accelerated course, treatment resistance and a dismal outcome. We have recently identified low catalase expression as a major antioxidant element that identifies an indolent clinical behavior in CLL. In contrast, high catalase expression is associated with a more aggressive disease course. However, the precise molecular mechanisms controlling catalase expression and activity are still poorly understood at both transcriptional and activity levels. The single nucleotide polymorphism (SNP) -262 C/T in the promoter region of the catalase (CAT) gene has been described to be associated with different levels of catalase in hepatocarcinoma and chronic myelogenous leukemia cell lines as well as in erythrocytes. The main objective of this study is to investigate regulatory mechanisms underlying differential expression of catalase in CLL patients’ prognostic subgroups. Specifically, this study aimed at characterizing the CAT SNP -262 C/T, which could be associated with differential expression of catalase in CLL. In leukemic cells isolated from 20 patients with CLL, we detected catalase expression levels using quantitative reverse transcription polymerase chain reaction (RT-PCR). Genotyping of the SNP -262 C/T (Id: rs1001179) in the promoter region of catalase was performed by PCR restriction fragment length polymorphism PCR-RFLP. Then, PCR products were digested by restriction endonuclease EcoR V and analyzed using gel electrophoresis. The CAT expression levels were compared between different genotypes using Student t test. We detected the homozygous CC genotype in 9/20 (45%) patients’ cells, the heterozygous CT genotype in 9/20 (45%) patients, whilst 2/20 (10%) individuals were homozygous for the mutant T-allele. The genotype frequencies in this population were in accordance with the Hardy–Weinberg equilibrium. Then, we compared the catalase expression levels between the groups of CLL samples exhibiting the CAT rs1001179 CC, and the CT/TT genotypes. Interestingly, cases harboring the TT and CT genotypes exhibited a significantly higher catalase expression compared with cells bearing the CC genotype. This study establishes a significant association between the -262 C/T SNP and catalase expression levels in CLL, thus indicating that CAT polymorphisms contribute to differential catalase expression in CLL patients with divergent clinical outcome. Our data represent the basis of future studies aimed at dissecting molecular mechanisms that regulate catalase expression and activity in CLL, which could be of crucial relevance for the development of therapies targeting redox pathways. We thank Gilead for funding support.